Conventionally known glycidoxy group-containing organosilicon compounds for use in the modification of interfacial properties of epoxy resins, polyesters, polyurethanes, polyamides, or polyimides include compounds of the following formula (II) having an organic group having a glycidoxy group at both ends of a dimethylsiloxane oligomer, and compounds of the following formula (III) having an organic group having one glycidoxy group at one end of a dimethylsiloxane oligomer. The compounds of formulas (II) and (III) are disclosed in, for example, JP-A-62-l92423. (The term "JP-A" as used herein means an "unexamined published Japanese patent application".) ##STR2## wherein Me represents a methyl group, and m represents a positive integer.
However, modification of a polymer by the compound of formula (II) has a problem that since the whole siloxane segment is introduced into the resulting polymer, the compound (II) should be used in a considerably large proportion for attaining sufficient modification of interfacial properties of the final resin molded articles. In the case of the compound of formula (III), there is a problem that since the compound is not a so-called bifunctional compound, a high molecular weight polymer is difficult to obtain or the compound (III) cannot be used as a crosslinking agent to crosslink organic polymer molecules.